1. Field of the Invention
The present invention relates to chairs, and particularly to chairs having backs that are adjustable to conform to the contour of a user's back.
2. Description of Related Art
In today's society, people spend an increasing amount of time sitting. The employment market is shifting from manufacturing jobs to information processing jobs. As a result, more and more people are employed in jobs which require a great deal of time sitting. Further, many people devote large amounts of leisure time to activities, such as watching television, which are usually done sitting.
Given the dramatic increase in the amount of time people spend sitting, it is important to provide chairs which are both comfortable and safe. One of the most important features of any chair is the manner in which it supports a user's back. If the chair provides inadequate support or supports the back in an improper position, the user may become uncomfortable after sitting for an extended period of time. Prolonged sitting in a chair with improper or inadequate back support may also contribute to fatigue, poor posture, and even chronic back problems. On the other hand, a chair which provides the proper type of support may avoid, or even help to correct, such problems.
People's backs are different in size, shape, and strength. Because each person's back has a unique configuration, each person's back has unique support requirements. As a result, the ideal back support will vary from individual to individual.
Unfortunately, chairs are typically designed with a back support sized and shaped for the average individual. In an effort to produce more comfortable and healthy seating, some chairs, particularly those commonly used in the office environment, are configured to allow adjustment of some features, such as the height and angle of the back support. However, the adjustable features in such chairs are limited. As a result, such chairs cannot provide everyone the proper fit and support.
A variety of chairs have been developed in attempts to improve on the comfort and support offered by standard office furniture. Typically this is done by increasing the number and types of adjustments which the user can make to the chair. For example, the chair described in U.S. Pat. No. 3,990,742 to Glass has a number of individual cam-like members extending laterally across the chair. These members can be individually rotated to modify the shape of the back support. Although this type of system offers increased adjustability, it sacrifices convenience. Given the number of cam members that must be adjusted for each user, it is impractical for a variety of users to use such a chair. U.S. Pat. No. 5,018,786 to Goldstein also describes a chair having a number of individually adjustable back support members. Again, given the large number of individual adjustments necessary to configure the chair to each user, this type of chair is ill-suited for the office environment.
Some chairs offer automatic adjustment systems. For example, U.S. Pat. No. 4,944,554 to Gross employs a number of motors to automatically adjust the configuration of a chair to a predetermined spinal profile. However, the complicated electrical and mechanical interfaces required for this type of chair limit its reliability, availability, and practicality in many environments.
In a few types of chairs, such as wheel chairs, it is not uncommon for the back support to be custom fit to the user. For example, U.S. Pat. No. 4,615,856 to Silverman, U.S. Pat. No. 4,828,325 to Brooks, and U.S. Pat. No. 4,890,235 to Reger all describe high quality customized chairs. However, each of these chairs has the common drawback of providing a permanently contoured surface that is suitable only for one particular user. As a result, such chairs do not offer the adjustability desirable to allow a wide variety of users to sit comfortably in the chair.